iOS 11.4 includes AirPlay 2 multi-room audio, support for HomePod stereo pairs, and Messages in iCloud. This update also includes bug fixes and improvements.

AirPlay 2 – Control your home audio system and AirPlay 2-enabled speakers throughout your house – Play music at the same time on multiple AirPlay 2-enabled speakers in your house, all in sync – Control AirPlay 2-enabled speakers from Control Center, the Lock screen, or AirPlay controls within apps on your iPhone or iPad – Use your voice to control AirPlay 2-enabled speakers with Siri from your iPhone or iPad, HomePod, or Apple TV – Take a call or play a game on your iPhone or iPad without interrupting playback on your AirPlay 2-enabled speakers

HomePod stereo pair – This update supports setting up your HomePod stereo pair using your iPhone or iPad – HomePod pair automatically senses its location in the room and balances the sound based on the speakers’ locations – Advanced beamforming provides wider soundstage than traditional stereo pair – HomePod will automatically update to support stereo pairs, unless auto updates are disabled in the Home app

Messages in iCloud – Store your messages, photos, and other attachments in iCloud and free up space on your devices – All your messages appear when you sign into a new device with the same iMessage account – When you delete messages and conversations they are instantly removed from all your devices – To turn on Messages in iCloud, enable Messages in iCloud settings (Settings > [your name] > iCloud) – Your conversations continue to be end-to-end encrypted

Other improvements and fixes – Enables teachers to assign their students reading activities in iBooks using the Schoolwork app – Fixes an issue where certain character sequences could cause Messages to crash – Addresses a Messages issue that could cause some messages to appear out of order – Addresses an issue that could prevent logging in or accessing files on Google Drive, Google Docs and Gmail in Safari – Fixes an issue that could prevent data syncing in Health – Fixes an issue that could prevent users from changing what apps can access Health data – Resolves an issue that could cause an app to appear in an incorrect location on the Home screen – Fixes an issue where CarPlay audio could become distorted – Fixes an issue where selecting music from your iPhone could fail when playing music over Bluetooth or when connected to USB on some vehicles